This page is a quick reference checkpoint for SUM OVER in IBM DB2: behavior, syntax rules, edge cases, and a minimal example; plus the official vendor documentation.
SUM OVER returns the running or partitioned sum within the window frame.
When no frame clause is specified, SUM() OVER(...) by default aggregates over the entire partition; window-aggregation-group defaults apply. Also: an OLAP specification cannot be used in WHERE, GROUP BY, HAVING, VALUES, SET, or as an argument to another aggregate. (As per Db2 for z/OS OLAP spec page)
If this behavior feels unintuitive, the tutorial below explains the underlying pattern step-by-step.
can use aggregate functions (like SUM) with an OVER() clause - i.e. as an OLAP aggregation specification
SELECT SUM(sales) OVER (PARTITION BY region) FROM sales_table;
If you came here to confirm syntax, you’re done. If you came here to get better at window functions, choose your next step.
SUM OVER is part of a bigger window-function pattern. If you want the “why”, start here: Aggregate Window Functions
Reading docs is useful. Writing the query correctly under pressure is the skill.
For the authoritative spec, use the vendor docs. This page is the fast “sanity check”.
View IBM DB2 Documentation →Looking for more functions across all SQL dialects? Visit the full SQL Dialects & Window Functions Documentation.